In certain applications, such as at the air intake of an engine or an air compressor, it has long been common practice to provide some sort of filtration apparatus, for removing dust, soot, sand, or other particulate matter from the intake air, in order to prevent the particulate matter from causing damage, and to promote long life of the engine or compressor. Such filtration apparatuses often include a tubular-shaped housing having an inlet for unfiltered air, and a clean air outlet, with the clean air outlet being operatively connected to the air intake of the engine or compressor. Such filter apparatuses also typically include a filter cartridge, having a filter pack formed from a filter media through which the air must flow in passing between the unfiltered air inlet and the clean air outlet of the filter apparatus.
Such filter apparatuses are also typically configured in such a manner that the filter cartridge may be removed for cleaning, or exchange, after a pre-determined operating time. For example, U.S. Pat. No. 5,730,769, to Dungs et al., discloses an air filter, for cleaning the combustion air for an internal combustion engine, having a cylindrical housing provided with an unfiltered air inlet and a clean air outlet, with the clean air outlet being mounted substantially concentrically on an axial end face of the housing. An extension tube extends into the housing at the clean air outlet. A filter insert, includes a radial packing on its end face, with the packing being configured to slide onto the center tube at the clean air outlet. The opposite end face of the filter insert is closed. The radial packing is provided with a sealing bead which is freely movable in the radial direction.
Experience has shown, however, that a sealing bead which is freely movable in the radial direction, as taught by Dungs, does not provide an adequate seal in some applications, particularly where the system must operate at a relatively high pressure differential across the filter cartridge, or under conditions where the interval between cleaning or exchange of the filter cartridge is long enough to cause the filter media of the filter cartridge to become dirty enough to create a high differential pressure across the filter cartridge. Experience has shown that this tendency of a freely movable radial seal to leak becomes more prevalent as the diameter of the seal is enlarged to provide increased flow capacity of a filter cartridge.
In an attempt to provide a seal configuration which is better suited for use in filters having increased flow capacity, while yet still providing some measure of compressibility in a radial direction, some prior filter elements, such as those shown in U.S. Pat. Nos. 6,149,700 and 6,306,193 B1, to Morgan et al., have provided an extended outer liner, surrounding the outer pleat tips of a pleated filter media, in such a manner that a portion of an end cap of resilient compressible material at an axial end of the filter element bears radially between, and is radially compressed between the outer liner and a flow tube, when the filter element is attached to a filter housing. The addition of the outer liner, as required in the Morgan '700, and '193 patents, for example, undesirably adds complexity and cost to the fabrication and disposal of expended filter elements. The Morgan patents also disclose that the outer liner be fabricated from an expanded wire mesh, or a screen, or from perforated metal. The use of such metallic components is particularly undesirable in filter elements which are designed, and/or required by governmental regulations, to be incinerable.
It is desirable, therefore, to provide an improved method and apparatus for reinforcing a seal in a filter apparatus, which overcomes one or more of the drawbacks of prior sealing method and apparatuses, discussed above, and also provides such an improved method and apparatus in a form conducive to providing increased flow capacity through a filter apparatus in which the invention is practiced.